Photocatalysis for Water Decomposition by RuO₂-Dispersed ZnGa₂O₄ with d¹⁰ Configuration

Abstract

The photocatalytic activity for water decomposition of RuO 2 -dispersed ZnGa 2 O 4 with an octahedrally coordinated Ga 3+ ion was studied in order to examine the photocatalytic properties of p-block metal oxides with d 10 configuration. ZnGa 2 O 4 was impregnated with Ru 3 (CO) 12 or Ru(C 5 H 7 O 2 ) 3 in THF and oxidized to convert them to RuO 2 . For RuO 2 -loaded ZnGa 2 O 4, hydrogen and oxygen were stably produced from the initial stage of reaction under Hg−Xe lamp light irradiation. The activity dependence on the calcination temperature of ZnGa 2 O 4, the amount of RuO 2 loaded, and the oxidation temperature of RuO 2 showed that the dispersion of small RuO 2 particles leads to high photocatalytic activity. The electronic structure of ZnGa 2 O 4 was calculated by a plane-wave-based density function theory (DFT). The valence bands were mainly composed of the O 2p orbitals, whereas the conduction bands were formed by hybridzation of Ga 4s4p and Zn 4s4p orbitals. Large dispersion observed in the conduction band indicated the large mobility of photoexcited electrons, which was considered to be responsible for high photocatalytic performance. The feature of electronic structures relating to photocatalysis was discussed in comparison with those of transition metal oxides.